digestive system

Question 1

2.30 where is bile produced?

Answer 1

the liver

Question 2

2.30 where is bile stored?

Answer 2

the gall bladder

Question 3

2.27 describe the structure & function of the human alimentary canal - what order does the food go through each organ?

Answer 3

• mouth
• oesophagus
• stomach
• duodenum (small intestine)
• ileum (small intestine)
• colon (large intestine)
• rectum (large intestine)
• anus

Question 4

2.27 describe structure & function of mouth/what happens in the mouth?

Answer 4

• ingestion takes place here
• digestion begins here - mechanical & chemical
• swallowing, flap called epiglottis which blocks food from entering the trachea

Question 5

what mechanical digestion happens in the mouth?

Answer 5

food broken up into smaller pieces in mouth by chewing. this inc SA for enzymes & also prevents discomfort when swallowing

Question 6

what chemical digestion happens in the mouth?

Answer 6

saliva released into mouth by salivary glands - makes food easier to swallow, & also contains enzyme amylase. amylase works best at neutral pH, so is denatured when it reaches stomach & stops working

Question 7

2.27 describe the structure and function of the oesophagus

Answer 7

• long tube that connects mouth to stomach
• food pushed down by peristalsis
• 2 sets of muscles push food down oesophagus: the circular muscles contract behind the bolus pushing it along, & when the longitudinal muscles contract they make oesophagus wider

Question 8

2.27 describe the structure and function of the stomach

Answer 8

• gastric glands in stomach wall secrete enzyme pepsin, which begins process of digesting proteins into peptides (shorter chains of amino acids)
• contraction of stomach wall causes mixing of contents of stomach, maximising contact between enzymes & food
• pepsin’s optimum conditions are acidic pH - conditions in stomach acidic due to release of HCl by gastric glands
• HCl has very low pH, kills many bacteria & fungi which may be present in food we eat

Question 9

2.27 describe the structure and function of the small intestine (duodenum)

Answer 9

• duodenum final site of chemical digestion
• pancreas makes several enzymes & secretes them into duodenum: trypsin, amylase & lipase
• duodenum wall also contains glands which make enzymes & secretes them into the duodenum: maltase & peptidase
• duodenum also contains bile, produced by liver & stored in gall bladder, then released into duodenum through bile duct

Question 10

2.27 describe the structure and function of the pancreas

Answer 10

• pancreas makes several enzymes & secretes them into duodenum: trypsin, amylase & lipase

Question 11

2.31 what is the role of bile?

Answer 11

1. neutralises stomach acid - enzymes in duodenum work best at pH 7-8
2. emulsifies lipids - breaks large droplets into smaller droplets, inc SA for lipase to digest fats

Question 12

2.27 describe the structure and function of the small intestine (ileum)

Answer 12

• once food entered ileum digestion over and absorption begins
• ileum has many folds & covered in finger like projections called villi
• it’s through these that small soluble molecules absorbed
• some absorbed by diffusion but some e.g. glucose also absorbed by active transport
• rate of diffusion inc by ileum’s adaptations

Question 13

2.32 how is the small intestine adapted for absorption?

Answer 13

rate of diffusion in ileum inc by it having:
- large SA: folding of ileum, villi and microvilli all inc SA
- short diffusion distance: villi walls are one cell thick
- high conc. gradient: provided by capillary network and lacteals removing absorbed molecules

Question 14

2.27 describe the structure and function of the large intestine (colon & rectum)

Answer 14

• colon site for all reabsorption of water
• faeces then stored in rectum & egested from anus

Question 15

what’s the definition for digestion?

Answer 15

the breakdown of large insoluble molecules into small soluble molecules

Question 16

what is ingestion?

Answer 16

taking food in through the mouth & swallowing

Question 17

what is absorption?

Answer 17

the movement of small soluble molecules out of the gut & into the blood by diffusion and AT

Question 18

what is egestion?

Answer 18

passing out undigested food through the anus

Question 19

definition of assimilation?

Answer 19

building larger biological molecules from the small soluble molecules, in all cells

Question 20

2.25 identify the sources and describe the functions of carbohydrate

Answer 20

food source - bread, potatoes, rice, cereals, fruit

function - fuel for respiration

Question 21

2.25 identify the sources and describe the functions of proteins

Answer 21

food source - meat, eggs, fish, quinoa, quorn

function - growth & repair of cells and tissues, fuel for respiration

Question 22

2.25 identify the sources and describe the functions of lipid (fats and oils)

Answer 22

food source - butter, cooking oil, cream, avocados

function - store of energy (thermal & electrical), insulation, fuel for respiration

Question 23

2.26 how do energy requirements vary with activity levels, age and pregnancy?

Answer 23

activity levels - will need more energy
age - teenagers need more energy for growth
pregnancy - need more energy

Question 24

2.25 identify the sources and describe the functions of vitamin A

Answer 24

function - making a chemical in the retina & also protects the surface of the eye

food source - fish liver oil, liver, butter, carrots

effect of deficiency - night blindness & damaged cornea

Question 25

2.25 identify the sources and describe the functions of vitamin C

Answer 25

function - needed for cells & tissues to stick together

effect of deficiency - scurvy

food source - fresh fruit & vegetables, orange

Question 26

2.25 identify the sources and describe the functions of vitamin D

Answer 26

function - needed to absorb calcium & phosphate ions from food

effect of deficiency - rickets, caused by weak bones

food source - dairy products, oily fish

Question 27

2.25 identify the sources and describe the functions of the mineral ion calcium

Answer 27

function - needed to form bones & teeth

food source - milk & dairy products, fish, fresh vegetables

deficiency disease - rickets

Question 28

2.25 identify the sources and describe the functions of the mineral ion iron

Answer 28

function - forms the part of haemoglobin which binds to oxygen

food source - red meat, liver, spinach

deficiency disease - anaemia

Question 29

2.25 identify the sources and describe the functions of water

Answer 29

• essential solvent (allows things to be dissolved into it)
• used to transport components of blood
• crucial for temp regulations (e.g. sweating)

Question 30

2.25 identify the sources and describe the functions of dietary fibre

Answer 30

• plant material that you cant digest, mainly chemical called cellulose
• helps movement of food through intestine, prevents constipation & bowel cancer

Question 31

2.28 how is food moved through the gut?

Answer 31

by peristalsis

Question 32

2.24 what should a balanced diet include?

Answer 32

appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre

Question 33

2.33B practical: investigate the energy content in a food sample

Answer 33

• measure 25cm³ water into a boiling tube
• record starting temp
• measure mass of foodstuff
• put sample of foodstuff onto mounted needle & light it on fire w Bunsen burner
• hold under boiling tube of water to heat it
• if food stops burning, needs to be relit until will no longer burn
• measure finishing temp or water & calculate temp change
• energy content calculated using: energy transferred per gram of food (J) = (mass of water (g) x temp change x 4.2)/mass of food sample (g)

Question 34

2.33B what’s the equation to find the energy content in a food sample?

Answer 34

energy transferred per gram of food (J) = (mass of water (g) x temp change x 4.2)/mass of food sample (g)